A comparator circuit may be used in an electronic system to compare two input currents or voltages and output an indication of which is greater. A typical comparator circuit is fabricated in an integrated circuit using field effect transistors or CMOS transistors. The output should ideally change state when the two changing inputs cross over at an equal level. However, variations in the transistors, such as the size or electrical properties, can unbalance the comparator circuit. For example, process variations during fabrication of the transistors can unbalance the transistors. As a result, the comparator circuit may be biased toward one of the inputs, so that the output changes state when one input is larger than the other rather than when the inputs are equal.